﻿// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;

namespace SharpKit.JavaScript.Ast
{
    /// <summary>
    /// Provides an interface to handle annotations in an object.
    /// </summary>
    public interface IAnnotatable
    {
        /// <summary>
        /// Gets all annotations stored on this IAnnotatable.
        /// </summary>
        IEnumerable<object> Annotations
        {
            get;
        }

        /// <summary>
        /// Gets the first annotation of the specified type.
        /// Returns null if no matching annotation exists.
        /// </summary>
        /// <typeparam name='T'>
        /// The type of the annotation.
        /// </typeparam>
        T Annotation<T>() where T : class;

        /// <summary>
        /// Gets the first annotation of the specified type.
        /// Returns null if no matching annotation exists.
        /// </summary>
        /// <param name='type'>
        /// The type of the annotation.
        /// </param>
        object Annotation(Type type);

        /// <summary>
        /// Adds an annotation to this instance.
        /// </summary>
        /// <param name='annotation'>
        /// The annotation to add.
        /// </param>
        void AddAnnotation(object annotation);

        /// <summary>
        /// Removes all annotations of the specified type.
        /// </summary>
        /// <typeparam name='T'>
        /// The type of the annotations to remove.
        /// </typeparam>
        void RemoveAnnotations<T>() where T : class;

        /// <summary>
        /// Removes all annotations of the specified type.
        /// </summary>
        /// <param name='type'>
        /// The type of the annotations to remove.
        /// </param>
        void RemoveAnnotations(Type type);
    }

    /// <summary>
    /// Base class used to implement the IAnnotatable interface.
    /// This implementation is thread-safe.
    /// </summary>
    [Serializable]
    public abstract class AbstractAnnotatable : IAnnotatable
    {
        // Annotations: points either null (no annotations), to the single annotation,
        // or to an AnnotationList.
        // Once it is pointed at an AnnotationList, it will never change (this allows thread-safety support by locking the list)

        object annotations;

        /// <summary>
        /// Clones all annotations.
        /// This method is intended to be called by Clone() implementations in derived classes.
        /// <code>
        /// AstNode copy = (AstNode)MemberwiseClone();
        /// copy.CloneAnnotations();
        /// </code>
        /// </summary>
        protected void CloneAnnotations()
        {
            ICloneable cloneable = annotations as ICloneable;
            if (cloneable != null)
                annotations = cloneable.Clone();
        }

        /// <summary>
        /// Removes all annotations.
        /// </summary>
        protected void ClearAnnotations()
        {
            annotations = null;
        }

        sealed class AnnotationList : List<object>, ICloneable
        {
            // There are two uses for this custom list type:
            // 1) it's private, and thus (unlike List<object>) cannot be confused with real annotations
            // 2) It allows us to simplify the cloning logic by making the list behave the same as a clonable annotation.
            public AnnotationList(int initialCapacity)
                : base(initialCapacity)
            {
            }

            public object Clone()
            {
                lock (this)
                {
                    AnnotationList copy = new AnnotationList(this.Count);
                    for (int i = 0; i < this.Count; i++)
                    {
                        object obj = this[i];
                        ICloneable c = obj as ICloneable;
                        copy.Add(c != null ? c.Clone() : obj);
                    }
                    return copy;
                }
            }
        }

        public virtual void AddAnnotation(object annotation)
        {
            if (annotation == null)
                throw new ArgumentNullException("annotation");
        retry: // Retry until successful
            object oldAnnotation = Interlocked.CompareExchange(ref this.annotations, annotation, null);
            if (oldAnnotation == null)
            {
                return; // we successfully added a single annotation
            }
            AnnotationList list = oldAnnotation as AnnotationList;
            if (list == null)
            {
                // we need to transform the old annotation into a list
                list = new AnnotationList(4);
                list.Add(oldAnnotation);
                list.Add(annotation);
                if (Interlocked.CompareExchange(ref this.annotations, list, oldAnnotation) != oldAnnotation)
                {
                    // the transformation failed (some other thread wrote to this.annotations first)
                    goto retry;
                }
            }
            else
            {
                // once there's a list, use simple locking
                lock (list)
                {
                    list.Add(annotation);
                }
            }
        }

        public virtual void RemoveAnnotations<T>() where T : class
        {
        retry: // Retry until successful
            object oldAnnotations = this.annotations;
            AnnotationList list = oldAnnotations as AnnotationList;
            if (list != null)
            {
                lock (list)
                    list.RemoveAll(obj => obj is T);
            }
            else if (oldAnnotations is T)
            {
                if (Interlocked.CompareExchange(ref this.annotations, null, oldAnnotations) != oldAnnotations)
                {
                    // Operation failed (some other thread wrote to this.annotations first)
                    goto retry;
                }
            }
        }

        public virtual void RemoveAnnotations(Type type)
        {
            if (type == null)
                throw new ArgumentNullException("type");
        retry: // Retry until successful
            object oldAnnotations = this.annotations;
            AnnotationList list = oldAnnotations as AnnotationList;
            if (list != null)
            {
                lock (list)
                    list.RemoveAll(type.IsInstanceOfType);
            }
            else if (type.IsInstanceOfType(oldAnnotations))
            {
                if (Interlocked.CompareExchange(ref this.annotations, null, oldAnnotations) != oldAnnotations)
                {
                    // Operation failed (some other thread wrote to this.annotations first)
                    goto retry;
                }
            }
        }

        public T Annotation<T>() where T : class
        {
            object annotations = this.annotations;
            AnnotationList list = annotations as AnnotationList;
            if (list != null)
            {
                lock (list)
                {
                    foreach (object obj in list)
                    {
                        T t = obj as T;
                        if (t != null)
                            return t;
                    }
                    return null;
                }
            }
            else
            {
                return annotations as T;
            }
        }

        public object Annotation(Type type)
        {
            if (type == null)
                throw new ArgumentNullException("type");
            object annotations = this.annotations;
            AnnotationList list = annotations as AnnotationList;
            if (list != null)
            {
                lock (list)
                {
                    foreach (object obj in list)
                    {
                        if (type.IsInstanceOfType(obj))
                            return obj;
                    }
                }
            }
            else
            {
                if (type.IsInstanceOfType(annotations))
                    return annotations;
            }
            return null;
        }

        /// <summary>
        /// Gets all annotations stored on this AstNode.
        /// </summary>
        public IEnumerable<object> Annotations
        {
            get
            {
                object annotations = this.annotations;
                AnnotationList list = annotations as AnnotationList;
                if (list != null)
                {
                    lock (list)
                    {
                        return list.ToArray();
                    }
                }
                else
                {
                    if (annotations != null)
                        return new object[] { annotations };
                    else
                        return Enumerable.Empty<object>();
                }
            }
        }
    }
}

